The proposed research seeks to clarify the role and importance of dietary and salivary proteins in caries development in humans. Objectives of this research include ascertaining: (1) whether utilization of human salivary proteins by Streptococcus mutans can be correlated with individual caries status, (2) the manner and extent to which dietary and salivary proteins can serve as sources of essential amino acids for dental plaque-forming organisms such as Streptococcus mutans, and, (3) the hydrolytic enzymes of these organisms responsible for protein degradation. Two interrelated types of studies will be conducted to achieve these objectives. First, the ability of Strep. mutans to use salivary p roteins, form individuals exhibiting differing degrees of caries activity, as a sole source of essential amino acids will be determined. Second, salivary anionic and cationic proteins from human whole saliva and dietary proteins will be tested for their growth promoting capacity. In addition, partially purified proteinases from Strep. mutans, and other oral streptococci, will be used in studies pertaining to the hydrolysis of peptides, as well as selected salivary and dietary proteins, to indicate the specificity of these proteinases toward such types of substrates. This information will contribute importantly to the further understanding of whether peptides and proteins of salivary or dietary origin play only a passive role in plaque pathogenicity, or whether their involvement is more direct and dynamic.